1. Field of the Invention
The invention relates to a battery-dedicated electrode foil for use in a positive electrode plate of a battery, a positive electrode plate, a battery, and a vehicle and a battery-equipped appliance that employ the battery as well as a manufacture method for the battery-dedicated electrode foil, and a manufacture method for the positive electrode plate.
2. Description of the Related Art
In recent years, along with the wide-spread use of portable electronic appliances, such as cellular phones, notebook type personal computers, video camcorders, etc., and vehicles, such as hybrid electric motor vehicles and the like, the demand for batteries for use as power sources for driving these devices is increasing. Among these batteries, there exist batteries that employ a positive electrode foil whose base material is an aluminum electrode foil. Examples of such batteries include a lithium-ion battery that employs a positive electrode plate formed by applying a Li compound-containing positive electrode active material to such an aluminum electrode foil.
However, on a surface of an aluminum electrode foil, an aluminum oxide layer as a non-conductor is usually formed as a natural process to a thickness of, for example, about 5 nm. Therefore, if a positive electrode active material is formed on such an aluminum electrode foil, the electroconductivity between the aluminum electrode foil and the positive electrode active material tends to be low. Besides, the aluminum oxide layer is not sufficiently corrosion-resistant, and there is a risk of corrosion being caused by a positive electrode active material paste applied thereto, or by an electrolyte solution in the battery. In conjunction with these drawbacks, Japanese Patent Application Publication No. 10-106585 (JP-A-10-106585) discloses that a carbon film is formed on a surface of an aluminum electrode foil (aluminum current collector) so as to improve corrosion resistance and electroconductivity. Besides, Japanese Patent Application Publication No. 11-250900 (JP-A-11-250900) discloses that an electroconductive coating layer made of carbon, platinum or gold is formed on a current collector after the surface of the current collector has been etched.
However, in the case where a carbon film is formed as in JP-A-10-106585 and JP-A-11-250900, an attempt to form the film by the sputtering process, which has high mass productivity, often results in formation of an insulating diamond-like carbon (DLC) film, and thus involves a risk of reducing the electroconductivity. The use of platinum or gold, on the other hand, is costly, and may not be practical.